1998/09/10 by Mark G. Allen, Michael A. Dopita, Zlatan I. Tsvetanov +1 · 4 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Emission spectrum #Excitation #Galaxies: Formation, Evolution, Phenomena #Galaxy #Ionization #Line (geometry) #Photoionization #Photon #Spectral line #astro-ph
paper · pdf · doi:10.1086/306718
55 pages, 49 figures, ApJ accepted September 9, 1998. Figures 1a-f are provided in jpeg format
arxiv created 1998/09/10 · openalex publication_date 1999/02/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
This paper presents long-slit spectral maps of the bicone-shaped extended narrow-line region (ENLR) in the Seyfert galaxy NGC 2992. We investigate the physical properties of the ENLR via emission-line diagnostics and compare the observations to shock and photoionization models for the excitation mechanism of the gas. The line ratios vary as a function of position in the ENLR, and the loci of the observed points on line ratio diagrams are shown to be most consistent with shock+precursor model grids. We consider the energetics of a nuclear ionizing source for the ENLR and perform the q -test in which the rate of ionizing photons from the nucleus is inferred from measurements of the density and ionization parameter. The q -test is shown to be invalid in the case of NGC 2992 because of the limitations of the [S II] λ6717/λ6731 density diagnostic. The excitation of the gas is shown to be broadly consistent with the kinematics, with higher [N II] λ6583/Hα present in the more dynamically active region. We also show that the pressure associated with the X-ray-emitting plasma may provide a large fraction of the pressure required to power the ENLR via shocks.